Relationships between specific root length and respiration rate of fine roots across stands and seasons in Chamaecyparis obtusa

Fine root respiration (R (r) ) is closely linked with fine root morphology, especially with specific root length (SRL), in short-term measurements in some tree species. However, whether these relationships are also valid across different stands and seasons is not yet known. This study aimed to investigate these relationships in the fine roots of Chamaecyparis obtusa. The R (r) , mean root diameter, and SRL of fine root segments of two C. obtusa stands were determined every three months over two years. We detected significant positive correlations between R (r) and SRL of fine root segments across the stands over two years. The relationship of R (r) with SRL was stronger than that with the mean diameter of fine roots. The slopes and intercepts for the R (r) and SRL relationships did not differ among stands and measurement times. Further, we proposed a simple approach for estimating CO2 flux from fine roots at the stand level based on SRL and confirmed that the ranges of estimated CO2 values were comparable with those of values reported using the conventional approach. The fine root morphology typified by SRL is a key variable in R (r) of fine roots and CO2 flux at the stand level.